Computing devices have become a ubiquitous part of everyday life. For example, most people carry and use personal computing devices (e.g., smartphones and tablets) throughout their daily activities. Unfortunately, computing devices (especially relatively small mobile devices) may be easily lost, temporarily misplaced, left unattended, or stolen. Since considerable amounts of sensitive data and/or services may be accessible through today's computing devices, a typical computing device may provide optional locking mechanisms to reduce the likelihood that an unauthorized user will gain access to the sensitive data and/or services.
Many locking mechanisms are time-based. For example, one common locking mechanism may lock a computing device if a user does not actively use the device for a given period of time. Unfortunately, conventional time-based locking mechanisms may provide poor security in many important scenarios. For example, a locking mechanism that locks a mobile computing device after a user has not actively used the mobile computing device for a relatively long period of time may not be effective if the device is lost, misplaced, or left unattended and then found by an unauthorized user before the period of time has expired. Even if a computing device is locked after a relatively short period of inactivity, such locking mechanisms may not be effective if the device is stolen when the user is actively using the device. In addition to poor security, conventional time-based locking mechanisms may also provide poor usability to many users. For example, users that check their devices frequently may be forced to authenticate many times throughout the day in order to unlock their devices. The instant disclosure, therefore, identifies and addresses a need for systems and methods for securing computing devices that are not in users' physical possessions.